The invention relates generally to strapping tools, and more particularly to electric powered strapping tools.
Electric strapping tools are known generally, as disclosed for example in U.S. Pat. No. 4,313,779, entitled xe2x80x9cAll Electric Friction Fusion Strapping Toolxe2x80x9d, assigned commonly herewith. The exemplary prior art electric tool comprises a reversible electric motor that drives a strap tensioning feed wheel when the motor operates in one direction and vibrates a friction welder when the motor operates in an opposite direction. The motor reverses direction when a tension arm pivoted by tensioned strap disposed over a portion thereof actuates a limit switch of the tension arm. Strap tension is controlled by adjusting a set screw relative to the limit switch, which permits more or less pivoting of the tension arm by the tensioned strap before actuation of the limit switch.
An object of the present invention is to provide novel electric strapping tools and methods therefor that overcome problems in and improve upon the prior art.
Another object of the invention is to provide novel electric strapping tools and methods therefor that are economical and reliable.
Another object of the invention is to provide novel electric strapping tools and methods therefor that produce less heat and that do not overheat.
A further object of the invention is to provide novel electric strapping tools and methods therefor having user adjustable tool parameter control knobs that isolate and protect corresponding control devices housed in the strap tensioning tool.
It is also an object of the invention to provide novel electric tensioning tools and methods therefor that are more readily separated from tensioned straps after fastening.
Another object of the invention is to provide novel electric strapping tools having an electronics module with a rotation sensor mounted adjacent the electric motor.
A more particular object of the invention is to provide novel electric strapping tools and methods therefor comprising an electric motor having an output shaft coupled to a feed wheel, a modulator circuit coupled to a power input of the electric motor, whereby strap tension depends upon electric power supplied to the electric motor by the modulator circuit.
Another more particular object of the invention is to provide novel electric strapping tools and methods therefor comprising an electric motor having a rotatable shaft with an end substantially transverse to the rotation axis thereof, a magnet disposed on the end of the shaft and offset from the rotation axis thereof, a magnetic field detector disposed near the shaft, whereby rotation of the shaft is detectable by the magnetic field detector.
Another more particular object of the invention is to provide novel electric strapping tools and methods therefor comprising an electric motor having an output shaft coupled to a feed wheel and to a welding jaw, whereby the electric motor rotates the feed wheel and vibrates the welding jaw when the shaft thereof rotates in the same direction.
Yet another more particular object of the invention is to provide novel electric strapping tools and methods therefor comprising a strapping tool parameter adjustment member or device having a rotatable stem disposed at least partially in a housing of the tool, a portion of the stem of the adjustment member disposed in an opening of the control knob, and an annular resilient member disposed between and frictionally engaged with the stem and the control knob.
Still another more particular object of the invention is to provide novel electric strapping tools and methods therefor comprising tensioning strap with a feed wheel driven by an electric motor, sensing rotational output of the electric motor with a rotation detector positioned near an armature or shaft thereof, reducing power supplied to the electric motor when the rotational output thereof is reduced to a predetermined level sensed by the rotation detector, and maintaining strap tension by supplying reduced power to the electric motor.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.